The present invention relates generally to a process and apparatus for making switch circuits and more particularly to a process and apparatus for making insert molded circuits from a lace curtain.
The process of making insert molded switch circuits as is presently used, provides a method or process wherein a large number of electrical circuits can be manufactured by using a single plate which has been stamped into what is known in the art as the "lace curtain." The lace curtain typically includes a plurality or network of different circuits which are joined together by a thin member (hereinafter referred to as an "interconnect member"), usually made of the same material as the circuits. The thin interconnect member allows a large number of circuits to be joined together in a single piece and facilitates the handling of the plurality of different circuits. Eventually, the lace curtain is inserted into a device which injects a plastic or an other engineering resin material to form a base for all of the circuits in the lace curtain.
The interconnect members which join the circuits of the lace curtain must be severed such that the desired individual circuits are formed. Typically, this is performed after the plastic has been injection molded around the lace curtain. The severing process is typically accomplished, as a secondary processing step, by cutting the lace curtain through holes in the plastic in the location where the undesired interconnect member is located. After the interconnect members have been severed, the connectors of the device may then be formed into the desired shape.
Insert molding switch circuits has become an increasingly popular method in view of the advantages over other available methods of making circuits. For example, alternative methods, which may use heat staking or soldering, degrade the flatness and/or otherwise deteriorate the dimensional integrity of a component. Insert molding on the other hand avoids the steps of heat staking or soldering. Insert molding eliminates the need for fasteners, adhesives and even some of the components themselves. Thus, insert molding is impervious to loosening and fastening corrosion. Additionally, insert molding provides devices with exceptional resistance to vibration, moisture and temperature extremes. Since the insert molded circuits comprise a heat conductive cross-section, the insert molded circuit provides dissipation of heat an order of magnitude greater than plated traces. This additional heat dissipation permits the insert molded circuit to carry more current in less board space. In addition, the tolerances obtained through the insert molding process which include fixing a solid conductor in a steel mold tool and then molding a resin around the insert are far greater than the tolerances offered by an assembly process.
Although the presently used insert molding method provides many obvious advantages, it is not without disadvantages. For example, when the interconnect members are to be cut or severed since the plastic has been injection molded over the lace curtain, the lace curtain must be cut as an additional or secondary cutting process.
Additionally, one popular use for insert molded electrical circuits is in the automotive industry. Insert molded circuits are used in devices such as the control units for electric windows of automobiles. Therefore, it is not uncommon for these devices to come into contact with fluids, for example rainwater or fluids from accidental spills of beverages. In this event, the fluid will short circuit the electrical connection which has been severed (the interconnect member). That is, the fluid will fill the gap at a location where an open circuit previously existed thereby causing an electrical connection in an undesired location.
To avoid such consequences, it would be desirable to separate each individual circuit before the injection of the plastic or resin material. This would involve first severing the individual circuits and then separately placing the circuits in the mold into which the plastic is to be injected. This process, however, has obvious disadvantages. Such a process requires a substantial amount of handling of each individual circuit piece. The individual circuit pieces have to be precisely placed in the desired location, by an operator or suitable machine. Thus, such a process would require a substantial amount of additional time, thereby reducing the efficiency in producing such circuits.
Therefore, in view of the above, it is a primary object of the present invention to provide an efficient method and apparatus for forming a plurality of individual circuits from a lace curtain comprising a network of circuits.
It is a further object of the present invention to provide an apparatus and method for manufacturing a circuit which may be formed from a lace curtain into a plurality of individual circuits wherein the interconnect members of the lace curtain are severed and an insulating material fills the gap.
It is still a further object of the present invention to provide an insert molding process and apparatus for the process wherein the finished insert molded circuit is resistant to shorts caused by fluids.